1. Field of the Invention
The present invention relates generally to the field of diagnostic radiology, and more particularly to a method and apparatus for the reduction of scatter in diagnostic radiology.
2. Description of the Prior Art
The contrast-reducing effect of scattered X-rays was recognized in the early days of radiography and led to the invention of the Bucky grid and its numerous improvements. The conventional Bucky grid consists of an array of lead foil strips which are separated by strips of radiolucent spacing material. The array is positioned between the object and image receptor so that the image-forming X-rays from the focal spot see only the edges of the foils strips and the majority pass through the radiolucent spacers. A significant portion (typically 30 - 45%), however, of the image-forming X-rays are attentuated by the lead strips. Scattered X-rays are emitted on the other hand from the patient in all directions and the majority of these that are emitted towards the image receptor do not have a straight line path through the radiolucent spacers to the image receptor and are therefore absorbed (typically 85 - 95%) in the lead.
The effect of the Bucky grid is to improve the quality of the X-ray image by attenuating scattered radiation to prevent it from reducing the image contrast. Although devices of this type are effective in improving image contrast, it remains poor in areas, such as the abdomen, where a higher degree of scattering exists. For example, even with the best Bucky grids, one obtains roughly only 53% of the primary beam contrast in normal X-rays of the abdomen. This low contrast level produces images of rather poor quality making accurate diagnosis of ailments based on these X-ray images extremely difficult.
Efforts have been made to improve image contrast through various techniques such as the use of air gaps, improved electronics and certain forms of scanning techniques. However, known techniques have generally proved to be unsatisfactory in obtaining high image qualities while maintaining rapid scanning rates and low exposure times. While it is possible to obtain high contrast images of good quality with very slow scanning speeds, as with a single scanning beam for example, such low speed scanning techniques are not practical in diagnostic radiology in view of the fact that body parts and organs move while patients are being X-rayed. Thus if relatively long exposure times are required to obtain X-ray images, the images are blurred to the extent of being useless for diagnosis due to the movements of the organs and body parts being X-rayed.
A need therefore exists for a practical method and apparatus and improving image contrast through scatter reduction in diagnostic radiology. To be truly practical, such a method and apparatus should be capable of use with existing equipment in view of the fact that any improvement which would require complete replacement of existing X-ray facilities simply for providing improved image quality would be expensive to an impractical degree, particularly in the current economic climate.